A new method of subsoil damping ratio identification based on free vibration of a massive concrete foundation

A new method of subsoil damping ratio identification based on law of conservation of energy is proposed. This method considers the whole time histories of vibration,differs from the traditional damping ratio identification method in the time domain which uses merely the amplitude to calculate damping ratio,and overcomes the defect of the traditional logarithmic decrement method for high accuracy requirement of amplitudes. The subsoil damping ratio of a massive concrete foundation is tested and calculated. The results of numerical simulation and actual test show that this method is of higher precision,stronger anti-noise ability and better stability compared with the traditional logarithmic decrement method. Even if the data acquisition is disturbed seriously by noise,the method proposed is effective and reliable.